Thermal power plants having a steam turbine are frequently equipped with a steam extraction, which provides thermal energy in order to operate another plant such as an industrial plant or a district heating system.
For example, U.S. Pat. No. 4,492,084 discloses a power plant comprising steam turbines and a steam extraction arranged in the cross-over pipe leading from the exhaust of an intermediate pressure steam turbine to the inlet of a low-pressure steam turbine. The extracted steam is used for a remote heating system having a heat exchanger and a reservoir, which provides heat during time periods of peak electric loads and reduced flow in the steam extraction. The remote heating system furthermore comprises lines to recirculate the heating medium from the reservoir to the heat exchanger for reheating.
US2008/0010968 discloses a steam power plant comprising multiple steam turbines on a single shaft and steam extractions at the exhausts of two double-flow intermediate-pressure steam turbines arranged in parallel. The steam extractions are connected with two heat exchangers arranged in series in a remote heating circuit. The arrangement allows the safe control of high flow volumes of heating steam.
In power plants as above-described the steam extractions are traditionally arranged for reasons of greater stability and safety at the bottom of the steam turbines, that is at the lower casing half-shell.